* The updates are underlined
All 6 units of Fukushima Daiichi Nuclear Power Station have been shut down.
Unit 1 (Shut down)
- Explosive sound and white smoke were confirmed after the big quake
occurred at 3:36 pm on March 12, 2011. It was assumed to be hydrogen
explosion.
- At 3:37 pm on March 25, 2011, we started injecting freshwater to the
reactor and are now injecting fresh water by a motor driven pump powered
by the off-site transmission line.
- At 10:11 am on December 10, 2011, in addition to water injection from
water feeding system, we started water injection from piping of core
spray system to the reactor.
The Current water injection volume is approx. 4.5 m3/h from the reactor
feed water system and approx. 1.9 m3/h from the core spray system.
- At 1:31 am on April 7, 2011, we commenced injection of nitrogen gas into
Primary Containment Vessel.
- At 11:22 am on August 10, 2011, we started cyclic cooling for the water
in the spent fuel pool by an alternative cooling equipment of the Fuel
Pool Cooling and Filtering System.
- On October 28, 2011, we completed installation of the cover for the
Reactor Building in order to contain dispersion of radioactive
substances.
- At 4:04 pm on November 30, 2011, we started operation to inject nitrogen
into the reactor pressure vessel.
- At 6:00 pm on December 19, 2011, a full-scale operation of the PCV gas
management system started.
Unit 2 (Shut down)
- At approximately 6:00 am on March 15, 2011, an abnormal noise began
emanating from nearby Pressure Suppression Chamber and the pressure
within the chamber decreased.
- At 10:10 am on March 26, 2011, we started injecting freshwater to the
reactor and are now injecting fresh water by a motor driven pump powered
by the off-site transmission line.
- At 2:59 pm on September 14, 2011, in addition to water injection from
water feeding system, we started water injection from piping of core
spray system to the reactor.
The Current water injection volume is approx. 6.0 m3/h from the reactor
feed water system and approx. 4.0 m3/h from the core spray system.
- At 5:21 pm on May 31, 2011, we started cyclic cooling for the water in
the spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- At 8:06 pm on June 28, 2011, we started injecting nitrogen gas into the
Primary Containment Vessel.
- At 6:00 pm on October 28, 2011, a full-scale operation of the PCV gas
management system started.
- At 10:46 am on December 1, 2011, we started the nitrogen injection to
the Reactor Pressure Vessel.
- At 11:50 am on January 19, 2012, we started the operation of the spent
fuel pool desalting facility.
Unit 3 (Shut down)
- Explosive sound and white smoke were confirmed at approximately 11:01 am
on March 14, 2011. It was assumed to be hydrogen explosion.
- At 6:02 pm on March 25, 2011, we started injecting fresh water to the
reactor and are now injecting fresh water by a motor driven pump powered
by the off-site transmission line.
- At 2:58 pm on September 1, 2011, we started water injection by core
spray system in addition to water injection by the reactor feed water
system piping arrangement.
The Current water injection volume is approx 5.0 m3/h from the reactor
feed water system and approx. 3.9 m3/h from the core spray system.
- At 7:47 pm on June 30, 2011, we started cyclic cooling for the water in
the spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System.
- At 8:01 pm on July 14, 2011, injection of nitrogen gas into the Primary
Containment Vessel started.
- At 4:26 pm on November 30, 2011, we started operation to inject nitrogen
into the reactor pressure vessel.
- At 3:18 pm on January 14, we started operation of the radioactive
material removal instrument for the spent fuel pool in Unit 3
Unit 4 (Outage due to regular inspection)
- At around 6 am on March 15, 2011, we confirmed the explosive sound and
the sustained damage around the 5th floor rooftop area of Reactor
Building.
- At 12:44 pm on July 31, 2011, we started cyclic cooling for the water in
the spent fuel pool by an alternative cooling equipment of the Fuel Pool
Cooling and Filtering System (from 1:30 pm to 3:14 pm on January 12,
2012, we injected hydrazine [corrosion inhibitor] in conjunction with
the cyclic cooling).
- At 10:58 am on November 29, 2011, in order to decrease more salinity, we
installed Ion exchange equipment and started the operation of such
equipment.
- At this moment, we don't think there is any reactor coolant leakage
inside the primary containment vessel.
Unit 5 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 5:00 am on March 19, 2011, we started the Residual Heat Removal
System Pump in order to cool the spent fuel pool.
- At 2:45 pm on July 15, 2011, we started the operation of the original
Residual Heat Removal System (System B) by its original seawater pump.
- At 10:11 am on December 22, 2011, since we finished the recovery work of
seawater pump (System B) of equipment water cooling system, we made a
trial run. At 11:25 am on the same day, we confirmed no abnormalities
and restarted the operation.
- At this moment, we don't think there is any reactor coolant leakage
inside the primary containment vessel.
Unit 6 (Outage due to regular inspection)
- Sufficient level of reactor coolant to ensure safety is maintained.
- At 10:14 pm on March 19, 2011, we started the Residual Heat Removal
System Pump of Unit 6 to cool down Spent Fuel Pool.
- At 2:33 pm on September 15, 2011, we started separately cooling the
reactor through the Residual Heat Removal System and the spent fuel pool
through Equipment Cooling Water System and Fuel Pool Cooling System.
- At this moment, we do not think there is any reactor coolant leakage
inside PCV.
Others
- At around 10:00 am on June 13, 2011, we started the operation of the
circulating seawater purification facility installed at the screen area
of Unit 2 and 3.
- At 8:00 pm on June 17, 2011, we started operation of Water Treatment
Facility against the accumulated water. At 6:00 pm on July 2, we started
the circulating injection cooling to inject the water, which was treated
by the accumulated water treatment system, to the reactors through the
buffer tank.
- At 7:41 pm on August 19, 2011, we started treatment of accumulated water
by parallel operation of one line from the cesium adsorption instrument
to the decontamination instrument and the other treatment line of the
cesium adsorption instrument No.2.
- At 2:06 pm on October 7, 2011, we started to spray purified accumulated
water brought from Unit 5 and 6 continually in order to prevent dust
scattering and potential fire outbreaks from the cut down trees.
- On October 28, 2011, we started installation of the water proof wall at
the sea side, in front of the existing shore protection, Units 1-4, in
order to contain marine pollution by underground water.
- At 12:25 pm on December 13, 2011, we started the re-circulating
operation of desalination facility (reverse osmosis membrane type) for
the purpose of suppression of condensed water after desalination
treatment.
- As finding of accumulated water containing radioactive materials at the
trench between the Process Main Building and the Miscellaneous Solid
Waste Volume Reduction Treatment Building [High Temperature Incinerator
Building] (December 18, 2011), we started the inspection of other
trenches at the site on January 11.
- At 9:42 on January 19, we started injecting water to unit 3 condensate
storage tank. At 6:00 pm on the same day, we finished filling water. At
9:05 am on January 21, we restarted filling water.
- At 3:37 pm on January 20, we started transferring accumulated water from
the basement, T/B, Unit 1 to the basement, T/B, Unit 2.
- At 3:23 pm on January 20, we started transferring accumulated water from
the basement of T/B, Unit 2 to the Central Radioactive Waste Treatment
Facility (Miscellaneous Solid Waste Volume Reduction Treatment Building
[High Temperature Incinerator Building]).
At 7:02 am on January 21, a worker from the cooperating company found
water leakage from the transfer piping at the large equipment hatch, T/B,
Unit 4.
We checked the work site and observed water leakage from a flange of the
piping to a valve unit. Part of water dripped to the floor outside of
the valve unit. At 7:48 am on the same date, we stopped the transfer
pump for the accumulated water. At 7:55 am, we confirmed that the
dripping of water stopped. The water was within the T/B and there was no
leakage to outdoor, no leakage to the sea. The volume of water dripped
to the floor of T/B was approx 2 liters. The surface dose rate was
0.1mSv/h. We believe that this was not high density contaminated water.
The location of the leak was at a flange of newly installed piping.
After installation of the piping, we checked leakage using water at the
vertical pit, Unit 1*. We estimate that that water was pushed out and
dripped to the floor. After that, from 1:58 pm to 2:49 pm, we conducted
flushing of the transfer piping and confirmed that there was no leakage.
We will check the flange and repair.
* water at the vertical pit, Unit 1: we estimate that this was a mixture
of seawater and rainwater. The measurement result on January 14 was as
below:
(I-131: below detectable limit [1.7 x 10-2Bq/cm3],
Cs-134: 1.8 x 10-1Bq/cm3, Cs-137: 2 x 10-1Bq/cm3)
- From 3:17 pm on January 20 to 2:18 pm on January 21, we transferred
accumulated water from the basement of T/B, Unit 3 to the Central
Radioactive Waste Treatment Facility (Miscellaneous Solid Waste Volume
Reduction Treatment Building [High Temperature Incinerator Building]).
As water leakage occurred on the piping for transferring accumulated
water from the basement of T/B, Unit 2 to the Central Radioactive Waste
Treatment Facility (Miscellaneous Solid Waste Volume Reduction Treatment
Building [High Temperature Incinerator Building]), we started checking
similar flanges to confirm leakage. At 2:30 pm, we found seepage at one
location (without water dripping). We will consider countermeasures such
as repair.
